What time will it be, step by step

Given a start and how long something lasts, when does it end?

The question

4:05 + 25 min

4:054:104:154:204:254:30 4:05
  1. It starts at 4:05 and runs for 25 minutes. Hop forwards along the line rather than adding the digits — then the hour never has to be carried.
  2. It all fits inside the one hour, so it is a single hop of 25 minutes — no o'clock to cross.
  3. So it ends at 4:30.

How it works.

  1. 01

    It starts at 4:05 and runs for 25 minutes. Hop forwards along the line rather than adding the digits — then the hour never has to be carried.

  2. 02

    It all fits inside the one hour, so it is a single hop of 25 minutes — no o'clock to cross.

  3. 03

    So it ends at 4:30.